US experts predict sea levels to rise by more than thought

WASHINGTON -- Global sea levels could rise two to three times higher over the next century than previous U.N. estimates, according to a study released Friday by the U.S. National Research Council (NRC).

A committee of experts evaluated the latest U.N. data and updated those projections with new data on polar ice-cap melting that is believed to be speeding up sea level rise around the world.

By 2100, the NRC estimates that global sea levels will rise between 20-55 inches (50 and 140 centimeters).

The U.N. Intergovernmental Panel on Climate Change's (IPCC) projection in 2007 had predicted a fraction of that, at 7 to 23 inches (18-59 centimeters) worldwide.

"Our answers are pretty much in line with what others have done except that the IPCC was a little timid in 2007 about the ice contribution, so using more current information about the ice melt we have a bigger contribution there," said Robert Dalrymple, committee chair and professor of civil engineering at Johns Hopkins University.

The wide range within each estimate is due to increasing uncertainty about sea level projections as researchers attempt to assess what may happen further and further into the future, the report said.

In the near term, the NRC predicted a global sea level rise of 3 to 9 inches (8 to 23 centimeters) by 2030 (over the 2000 level) and seven to 19 inches (18 to 48 centimeters) by 2050.

The committee was convened by an executive order from the state of California to assess sea level rise in order to inform preparations for coastal impact, and to make detailed predictions for the U.S. West Coast.